Modulation of nitrosative stress via glutathione-dependent formaldehyde dehydrogenase and S-nitrosoglutathione reductase.

Glutathione-dependent formaldehyde dehydrogenase (GFD) from Taiwanofungus camphorata plays important roles in formaldehyde detoxification and antioxidation. The enzyme is bifunctional. In addition to the GFD activity, it also functions as an effective S-nitrosoglutathione reductase (GSNOR) against nitrosative stress. We investigated the modulation of HEK (human embryonic kidney) 293T cells under nitrosative stress by transfecting a codon optimized GFD cDNA from Taiwanofungus camphorata (Tc-GFD-O) to these cells. The parental and transfected HEK 293T cells were then subjected to S-nitrosoglutathione treatment to induce nitrosative stress. The results showed that in Tc-GFD-O-transfected 293T cells, the expression and activity of GFD increased. Additionally, these cells under the nitrosative stress induced by S-nitrosoglutathione showed both higher viability and less apoptosis than the parental 293T cells. This finding suggests that the Tc-GFD-O in HEK 293T cells may provide a protective function under nitrosative stress.

A peroxiredoxin cDNA from Taiwanofungus camphorata: role of Cys31 in dimerization.

Peroxiredoxins (Prxs) play important roles in antioxidant defense and redox signaling pathways. A Prx isozyme cDNA (TcPrx2, 745 bp, EF552425) was cloned from Taiwanofungus camphorata and its recombinant protein was overexpressed. The purified protein was shown to exist predominantly as a dimer by sodium dodecyl sulfate-polyacrylamide gel electrolysis in the absence of a reducing agent. The protein in its dimeric form showed no detectable Prx activity. However, the protein showed increased Prx activity with increasing dithiothreitol concentration which correlates with dissociation of the dimer into monomer. The TcPrx2 contains two Cys residues. The Cys(60) located in the conserved active site is the putative active peroxidatic Cys. The role of Cys(31) was investigated by site-directed mutagenesis. The C31S mutant (C(31) → S(31)) exists predominantly as a monomer with noticeable Prx activity. The Prx activity of the mutant was higher than that of the corresponding wild-type protein by nearly twofold at 12 µg/mL. The substrate preference of the mutant was H2O2 > cumene peroxide > t-butyl peroxide. The Michaelis constant (K M) value for H2O2 of the mutant was 0.11 mM. The mutant enzyme was active under a broad pH range from 6 to 10. The results suggest a role of Cys(31) in dimerization of the TcPrx2, a role which, at least in part, may be involved in determining the activity of Prx. The C(31) residue does not function as a resolving Cys and therefore the TcPrx2 must follow the reaction mechanism of 1-Cys Prx. This TcPrx2 represents a new isoform of Prx family.

Biochemical characterization of a functional recombinant aryl-alcohol dehydrogenase from Taiwanofungus camphorata.

BACKGROUND: Aryl-alcohol dehydrogenases (AADs) have been known to involve in the metabolism of aromatic compounds. RESULTS: One TcAAD cDNA (GenBank HQ453361) encoding a putative aryl-alcohol dehydrogenase (AAD) was cloned from Taiwanofungus camphorata. The deduced amino acid sequence is conserved among the reported AADs. A 3-D structural model of the TcAAD has been created based on the known structure of voltage-dependent potassium channels subunit beta-2 (PDB code: 3EAU). To characterize the TcAAD, the coding region was subcloned into an expression vector and transformed into Saccharomyces cerevisiae. The recombinant His6-tagged TcAAD was overexpressed and purified by Ni affinity chromatography. The purified enzyme showed a band of approximately 39 kDa on a 12% SDS-PAGE. The molecular mass determined by MALDI-TOF is 40.58 kDa which suggests that the purified enzyme is a monomeric enzyme. Using veratraldehyde as a substrate, the KM, Vmax of TcADD was determined at pH 6.0. Using benzyl alcohol derivatives as substrates, the oxidizing power of TcADD via NAD+ at pH 9.6 was studied. CONCLUSIONS: The coding sequence of the TcAAD cDNA was introduced into an S. cerevisiae expression system and the active enzyme purified and characterized. Understanding the properties of this TcAAD will be beneficial for its potential in xenobiotic detoxification or production of natural flavors.

Molecular cloning and characterization of a thioredoxin from Taiwanofungus camphorata.

BACKGROUND: Thioredoxin (Trx) is reduced by thioredoxin reductase. Trx is used in ribonucleoide reduction, assimilatory sulfate reduction, in modulation of protein sulfhydryl groups, and refolding proteins. RESULTS: A TcTrx (Tc: Taiwanofungus camphorata) cDNA (640 bp, GenBank AY838902.1) encoding a putative thioredoxin (Trx) of 135 amino acid residues with calculated molecular mass of 16.17 kDa was cloned from Taiwanofungus c amphorata. The deduced amino acid sequence containing a motif (Cys-Gly-Pro-Cys) that is highly conserved among the reported Trxs. A three dimensional structural model of the TcTrx has been created based on the known structure of Malassezia sympodialis Trx (MsTrx, PDB ID: 2j23). To characterize the TcTrx, the codon optimized coding region was subcloned into an expression vector and transformed into Saccharomyces cerevisiae. The recombinant His8-tagged TcTrx was expressed and purified by Ni affinity chromatography. The purified enzyme showed a band of approximately 32 kDa (expected dimeric form) on a 12% SDS-PAGE. The molecular mass determined by MALDI-TOF is 33.16 kDa which suggests that the purified enzyme is a dimeric enzyme. Furthermore, the enzyme exhibited TcTrx activity via insulin assay. The Michaelis constant (K M ) value for insulin was 3.78 × 10-2 mM. The enzyme's half-life of deactivation was 13 min at 45°C. The enzyme was most active at pH 7. CONCLUSIONS: A three dimensional structural model of T. camphorata Trx based on its TcTrx cDNA sequence. The active form of the TcTrx has been successfully expressed in yeast. The enzyme possesses Trx activity and is capable of reduction of disulfide bonds during the formation of newly synthesized proteins.

Lemon protein disulfide isomerase: cDNA cloning and biochemical characterization.

BACKGROUND: Protein disulfide isomerases (PDIs), a family of structurally related enzymes, aid in protein folding by catalyzing disulfide bonds formation, breakage, or isomerization in newly synthesized proteins and thus. RESULTS: A ClPDI cDNA (1828 bp, GenBank accession HM641784) encoding a putative PDI from Citrus limonum was cloned by polymerase chain reaction (PCR). The DNA sequence encodes a protein of 500 amino acids with a calculated molecular mass of 60.5 kDa. The deduced amino acid sequence is conserved among the reported PDIs. A 3-D structural model of the ClPDI has been created based on the known crystal structure of Homo sapiens (PDB ID: 3F8U_A). The enzyme has two putative active sites comprising the redox-active disulfides between residues 60-63 and 405-408 (motif CGHC). To further characterize the ClPDI, the coding region was subcloned into an expression vector pET-20b (+), transformed into E. coli Rosetta (DE3)pLysS, and recombinant protein expressed. The recombinant ClPDI was purified by a nickel Sepharose column. PDI's activity was assayed based on the ability of the enzyme to isomerize scrambled RNase A (sRNase A) to active enzyme. The KM, kcat and kcat/KM values were 8.3 × 10-3 µM, 3.0 × 10-5 min-1, and 3.6 × 10-1 min-1 mM-1. The enzyme was most active at pH 8. CONCLUSIONS: The advantage of this enzyme over the PDI from all other sources is its low KM. The potential applications of this PDI in health and beauty may worth pursuing.

Taiwanofungus camphorata nitroreductase: cDNA cloning and biochemical characterisation.

Nitroreductases (Nrs) play important roles in redox system via NADPH or NADH as a reductant. A TcNr cDNA encoding a putative Nr was cloned from Taiwanofungus camphorata. A 3-D structural model of the TcNr has been created based on the known structure of BcNr (Bacillus cereus). To characterise the TcNr, the coding region was subcloned into an expression vector and transformed into Escherichia coli. The recombinant His(6)-tagged TcNr was purified by Ni affinity chromatography. The purified enzyme showed a single band at molecular mass of approximately 25 kDa on 12% sodium dodecyl sulphate-polyacrylamide gel electrophoresis. The enzyme exhibited Nr activity via ferricyanide assay. The Michaelis constant (K(M)) value for ferricyanide was 0.86 mM. The enzyme(')s half-life of deactivation at 45°C was 12.3 min. The enzyme was most active at pH 6. The enzyme's preferred substrate is 1-chloro-2, 4-dinitrobenzene.

Plastidial starch phosphorylase in sweet potato roots is proteolytically modified by protein-protein interaction with the 20S proteasome.

Post-translational regulation plays an important role in cellular metabolism. Earlier studies showed that the activity of plastidial starch phosphorylase (Pho1) may be regulated by proteolytic modification. During the purification of Pho1 from sweet potato roots, we observed an unknown high molecular weight complex (HX) showing Pho1 activity. The two-dimensional gel electrophoresis, mass spectrometry, and reverse immunoprecipitation analyses showed that HX is composed of Pho1 and the 20S proteasome. Incubating sweet potato roots at 45°C triggers a stepwise degradation of Pho1; however, the degradation process can be partially inhibited by specific proteasome inhibitor MG132. The proteolytically modified Pho1 displays a lower binding affinity toward glucose 1-phosphate and a reduced starch-synthesizing activity. This study suggests that the 20S proteasome interacts with Pho1 and is involved in the regulation of the catalytic activity of Pho1 in sweet potato roots under heat stress conditions.

An arsenate reductase homologue possessing phosphatase activity from sweet potato (Ipomoea batatas [L.] Lam): kinetic studies and characterization.

A cDNA encoding a putative arsenate reductase homologue (IbArsR) was cloned from sweet potato (Ib). The deduced protein showed a high level of sequence homology (16-66%) with ArsRs from other organisms. A 3-D homology structure was created based on AtArsR (PDB code 1T3K ) from Arabidopsis thaliana. The putative active site of protein tyrosine phosphatase (HC(X)(5)R) is conserved in all reported ArsRs. IbArsR was overexpressed and purified. The monomeric nature of the enzyme was confirmed by 15% SDS-PAGE and molecular mass determination of the native enzyme via ESI Q-TOF. The IbArsR lacks arsenate reductase activity but possesses phosphatase activity. The Michaelis constant (K(M)) value for p-nitrophenyl phosphate (pNPP) was 11.11 mM. The phosphatase activity was inhibited by 0.5 mM sodium arsenate [As(V)]. The protein's half-life of deactivation at 25 °C was 6.1 min, and its inactivation rate constant K(d) was 1.1 × 10(-1) min(-1). The enzyme was active in a broad pH range from 4.0 to 11.0 with optimum activity at pH 10.0. Phosphatase would remove phosphate group from nucleic acid or dephosphorylation of other enzymes as regulation signaling.

Monothiol glutaredoxin cDNA from Taiwanofungus camphorata: a novel CGFS-type glutaredoxin possessing glutathione reductase activity.

Glutaredoxins (Grxs) play important roles in the redox system via reduced glutathione as a reductant. A TcmonoGrx cDNA (1039 bp, EU158772) encoding a putative monothiol Grx was cloned from Taiwanofungus camphorata (formerly named Antrodia camphorata). The deduced amino acid sequence is conserved among the reported monothiol Grxs. Two 3-D homology structures of the TcmonoGrx based on known structures of human Grx3 (pdb: 2DIY_A) and Mus musculus Grx3 (pdb: 1WIK_A) have been created. To characterize the TcmonoGrx protein, the coding region was subcloned into an expression vector pET-20b(+) and transformed into E. coli C41(DE3). The recombinant His6-tagged TcmonoGrx was overexpressed and purified by Ni(2+)-nitrilotriacetic acid Sepharose. The purified enzyme showed a predominant band on 10% sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The enzyme exhibited glutathione reductase (GR) activity via dithionitrobenzoate (DTNB) assay. The Michaelis constant (K(M)) values for GSSG and NADPH were 0.064 and 0.041 mM, respectively. The enzyme's half-life of deactivation at 60 °C was 10.5 min, and its thermal inactivation rate constant (k(d)) was 5.37 × 10(-2) min(-1). The enzyme was active under a broad pH range from 6 to 8. The enzyme retained 50% activity after trypsin digestion at 37 °C for 40 min. Both mutants C(40)→S(40) and C(165)→S(165) lost 40-50% GR activity, whereas the mutant S(168)→C(168) showed a 20% increase in its GR activity.

Cloning, expression, and characterization of a thioredoxin reductase cDNA from Taiwanofungus camphorata.

A cDNA encoding putative thioredoxin reductase (TR) was identified from a medicinal mushroom, Taiwanofungus camphorata (T. camphorata). Alignment of the deduced amino acid sequence with TRs from other organisms showed high levels of identity (59-74%). A three-dimensional (3-D) homology structure was created for this TR. Functional T. camphorata TR (TcTR) was overexpressed in yeast and purified. The purified enzyme showed a monomic form on a 10% sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The enzyme's half-life of deactivation at 60 degrees C was 12.9 min, and its thermal inactivation rate constant K(d) was 5.37 x 10(-2) min(-1). The optimal pH for the enzyme was pH 8 and retained about 76% activity in the presence of 0.1 M imidazole. The enzyme showed 50% activity after 10 min of incubation at 37 degrees C with chymotrypsin. The Michaelis constant (K(m)) value for dithionitrobenzoate (DTNB) was 1.59 mM.

Cloning, expression, and characterization of an enzyme possessing both glutaredoxin and dehydroascorbate reductase activity from Taiwanofungus camphorata.

Glutaredoxins (Grxs) play important roles in the reduction of disulfides via reduced glutathione as a reductant. A cDNA (503 bp, EU193660) encoding a putative Grx was cloned from Taiwanofugus camphorata (Tc). The deduced amino acid sequence is conserved among the reported dithiol Grxs. A 3D homology structure was created for this TcGrx. To characterize the TcGrx enzyme, the coding region was subcloned into an expression vector pET-20b(+) and transformed into Escherichia coli . Functional TcGrx was expressed and purified by Ni(2+)-nitrilotriacetic acid Sepharose. The purified enzyme showed bands of approximately 15 kDa on 15% sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The TcGrx encodes a protein possessing both Grx and dehydroascorbate reductase (DHAR) activity. The Michaelis constant (K(m)) values for beta-hydroxyethyl disulfide (HED) and dehydroascorbate (DHA) were 0.57 and 1.85 mM, respectively. The half-life of deactivation of the protein at 100 degrees C was 8.5 min, and its thermal inactivation rate constant K(d) was 6.52 x 10(-2) min(-1). The enzyme was active under a broad pH range from 6.0 to 10.0 and in the presence of imidazole up to 0.4 M. The enzyme was susceptible to SDS denaturation and protease degradation/inactivation.

Characterization, molecular modelling and developmental expression of zebrafish manganese superoxide dismutase.

A 977 bp cDNA containing an open reading frame encoding 224 amino acid residues of manganese superoxide dismutase was cloned from zebrafish (zMn-SOD). The deduced amino acid sequence showed high identity with the sequences of Mn-SODs from human (85.1%) to nematode (61.6%). The 3-D structure model was superimposed on the relative domains of human Mn-SOD with the root mean square (rms) deviation of 0.0919 A. The recombinant mature zMn-SOD with enzyme activity was purified using His-tag technique. The half-life of the enzyme is approximately 48 min and its thermal inactivation rate constant k(d) is 0.0154 min(-1)at 70 degrees C. The enzyme was active under a broad pH (2.2-11.2) and in the presence of up to 4% SDS. Real-time RT-PCR assay was used to detect the zMn-SOD mRNA expression during the developmental stages following a challenge with paraquat. A high level expression of Mn-SOD mRNA was detected at the cleavage stage, but decreased significantly under paraquat treatment. The results indicated that Mn-SOD plays an important role during embryonic development.

Cloning, expression, and purification of a functional glutathione reductase from sweet potato (Ipomoea batatas [L.] Lam): kinetic studies and characterization.

A cDNA encoding a putative glutathione reductase (GR) was cloned from sweet potato (Ib). The deduced protein showed high level of sequence homology with GRs from other plants (79-38%). A three-dimensional (3-D) homology structure was created. The active site Cys residues are conserved in all reported GR. Functional IbGR was overexpressed and purified. The purified enzyme showed an active monomeric form on a 10% native polyacrylamide gel electrophoresis (PAGE). The monomeric nature of the enzyme was confirmed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and molecular mass determination of the native enzyme. The Michaelis constant (K(m)) values for GSSG (glutathione disulfide) and NADPH (ß-nicotinamide adenine dinucleotide phosphate, reduced form) were 0.114 and 0.056 mM, respectively. The enzyme activity was inhibited by Cu(2+) and Zn(2+), but not by Ca(2+). The protein's half-life of deactivation at 70 °C was 3.3 min, and its thermal inactivation rate constant K(d) was 3.48 × 10(-1) min(-1). The enzyme was active in a broad pH range from 6.0 to 11.0 and in the presence of imidazole up to 0.8 M. The native enzyme appeared to be resistant to digestion by trypsin or chymotrypsin.

Dehydroascorbate reductase cDNA from sweet potato (Ipomoea batatas [L.] Lam): expression, enzyme properties, and kinetic studies.

A cDNA encoding a putative dehydroascorbate reductase (DHAR) was cloned from sweet potato. The deduced protein showed a high level of sequence homology with DHARs from other plants (67 to approximately 81%). Functional sweet potato DHAR was overexpressed and purified. The purified enzyme showed an active monomeric form on a 12% native PAGE. The protein's half-life of deactivation at 50 degrees C was 10.1 min, and its thermal inactivation rate constant K(d) was 6.4 x 10(-2) min(-1). The enzyme was stable in a broad pH range from 6.0-11.0 and in the presence of 0.8 M imidazole. The K(m) values for DHA and GSH were 0.19 and 2.38 mM, respectively.

Molecular cloning and tissue distribution of three estrogen receptors from the cyprinid fish Varicorhinus barbatulus.

We present molecular cloning and tissue expression analysis of three estrogen receptor (ER) subtypes, vbERalpha, vbERbeta1 and vbERbeta2, from liver of the cyprinid fish Varicorhinus barbatulus through reverse transcription-polymerase chain reaction (RT-PCR) and rapid amplification of cDNA ends (RACE). The sequence alignment and phylogenetic analysis reconfirmed the evolutionary relationship of V. barbatulus within the family Cypriniformes. Directional constraints for subtype-specific substitution of critical amino acids were observed in the E2 binding region. For amino acid substitution, vbERbeta exhibited a M517L change in the ligand-dependent transactivation region. The tissue distributions were investigated using RT-PCR with subtype-distinguishable primers. Both vbERalpha and vbERbeta1 were most highly expressed in liver, while vbERbeta2 was higher in intestine. Here we demonstrate that the identification and cloning of ER subtypes using PCR is feasible in wildlife in that the temporal and spatial observations are consistent with those from phylogeny analysis and crystal structural investigation by others.

Human manganese superoxide dismutase suppresses HER2/neu-mediated breast cancer malignancy.

The up-regulation of HER2/neu is associated with human malignancies and is a useful target for developing anticancer drugs. Overexpression of human manganese superoxide dismutase (MnSOD) has been demonstrated to effectively suppress various carcinoma cells, including breast carcinomas, in vitro and in vivo. This study demonstrates that MnSOD effectively suppresses HER2/neu oncogene expression at the transcriptional level. Additionally, stable transfection was used and the MnSOD-transfected human breast cancer clones were found to be able to down-regulate the endogenous production of p185(HER2/neu). Furthermore, the MnSOD-overexpressing stable transfectants exhibited reduced soft-agarose colony-forming ability and metastatic properties, unlike control cell lines. These data suggest that MnSOD may be useful in treating HER2/neu-mediated human breast tumor malignancy.

A highly stable cambialistic-superoxide dismutase from Antrodia camphorata: expression in yeast and enzyme properties.

A cDNA encoding a putative superoxide dismutase (SOD) was identified in expressed sequence tags of Antrodia camphorata, a medicinal mushroom found only in Taiwan. The deduced protein was aligned with Mn-SODs and Fe-SODs from other organisms, this SOD showed greater homology to Mn-SOD. Functional A. camphorata SOD protein was overexpressed in yeast and purified. The purified enzyme showed two active forms on a 12.5% native PAGE, a dimer and a monomer. The dimeric protein's half-life of deactivation at 80 degrees C was 7 min, and its thermal inactivation rate constant K(d) was 9.87 x 10(-2)min(-1). The enzyme was stable in a broad pH range from 5-11; in the presence of 0.4M imidazole and 2% SDS. The atomic absorption spectrometric assay showed that 1.0 atom of manganese/iron (9:1) was present in each SOD subunit. The high stability of the enzyme make it better suited than other cambialistic-SODs for use in cosmetics. The SOD also documents its future utility in developing anti-inflammatory agent and in the treatment of chronic diseases.

Replacement of buried cysteine from zebrafish Cu/Zn superoxide dismutase and enhancement of its stability via site-directed mutagenesis.

Zebrafish Cu/Zn-superoxide dismutase (ZSOD1) has one free cysteine (Cys-7) in a first beta-strand with lower thermostability. We predicted the stability would be increased with single-point mutation at 70 degrees C via the I-Mutant 2.0 server, and generated a mutant SOD with replacement of the free Cys to Ala (ZSODC7A) by site-directed mutagenesis. The mutant was expressed and purified from the Escherichia coli strain AD494(DE3)pLysS and the yield was 2 mg from 0.4 L of culture. The ZSODC7A was heated at 90 degrees C. In a time-dependent assay, the time interval for 50% inactivation was 32 min, and its thermal inactivation rate constant K (d) was 2 x 10(-2) min(-1). The mutant was still activated in broad pH range (2.3-12), and had only a moderate effect under sodium dodecyl sulfate treatment. The calculated specific activity of the mutant was 3980 U/mg, twice that of wild-type ZSOD1. In addition, we soaked fish larva with equal enzyme units of either ZSOD1 or ZSODC7A for 2 h, and then stressed them with 100 ppm of paraquat to induce oxidative injury. The survival rate was significant.

A fused selenium-containing protein with both GPx and SOD activities.

As a safeguard against oxidative stress, the balance between the main antioxidant enzymes including superoxide dismutase (SOD), glutathione peroxidase (GPx), and catalase (CAT) was believed to be more important than any single one, for example, dual-functional SOD/CAT enzyme has been proved to have better antioxidant ability than either single enzyme. By combining traditional fusion protein technology with amino acid auxotrophic expression system, we generated a bifunctional enzyme with both GPx and SOD activities. It displayed better antioxidant ability than GPx or SOD. Such dual-functional enzymes could facilitate further studies of the cooperation of GPx and SOD and generation of better therapeutic agents.

Molecular cloning and functional expression of bovine deoxyhypusine hydroxylase cDNA and homologs.

Deoxyhypusine hydroxylase is the second of the two enzymes that catalyzes the maturation of eukaryotic initiation factor 5A (eIF5A). The mature eIF5A is the only known protein in eukaryotic cells that contains the unusual amino acid hypusine (N(epsilon)-(4-amino-2(R)-hydroxybutyl)lysine). Synthesis of hypusine is essential for the function of eIF5A in eukaryotic cell proliferation and survival. Here, we describe the cloning and characterization of bovine deoxyhypusine hydroxylase cDNA and its homologs. The deduced bovine deoxyhypusine hydroxylase protein is 87% identical to human enzyme and 45% identical to yeast enzyme. The overexpressed enzyme showed activity in catalyzing the hydroxylation of the deoxyhypusine residue in the eIF5A intermediate. An amino acid substitution from Glu 57 to Gly located at one of the four conserved His-Glu (HE) pairs, the potential metal coordination sites, resulted in severe reduction of deoxyhypusine hydroxylase activity. A deletion at the HEAT-repeats 1-3 resulted in complete losses of deoxyhypusine hydroxylase activity.